It's sad, but the age of consent in many states is 16. At that point, law enforcement can do nothing. Some of my daughter's friends in Kentucky had sex when they were 14 -- one is pregnant. My daughter will be 16 in Feb, but as far as I know she hasn't even had a serious boyfriend. That is way too young to start this type of relationship, but most kids these days see sex as entertainment, just like video games. Parents need to instill some values in their children.
My ex-wife also started young, but I didn't. I have challenged my daughter to wait at least as long as I did (she knows how old I was, because her mom and I told her). If she can wait that long, or until she is married, I will be very proud of her.
The sad thing is, these creeps will prey on young innocents like this. They have experience and know how to get a girl/woman in the mood. They take advantage of their weaknesses, and once they have tasted the fruit, then they can't get enough of it. Sex is almost like a drug to many, and they will do anything to get it.
The parents in this case did what they could to end the relationship, but in the end, they gave consent to save the family. Some may debate whether that was right or not, but with many teens the more you resist them the more determined they become. At least the parental bond is still intact and if things go badly, the girl can return home, knowing her parents care about her.